The human body generates static and time-varying electromagnetic fields which may be measured and used in numerous applications. However, these fields are often faint, even in close proximity to the body, and attenuate as the distance from the human body is increased. For example, ionic currents within neurons of the brain will generate voltage fluctuations and magnetic fields during synaptic transmission. While these fields have proved challenging to accurately measure, some approaches exist for directly detecting the electrical activity produced by the body. Typically, numerous electrodes are arranged to measure voltages at a patient's scalp with electroencephalography (EEG), or highly sensitive magnetometers are employed during magnetocephalography (MEG) to detect magnetic fields. Other techniques, such as functional magnetic resonance imaging (f-MRI), are able to indirectly measure electrical activity via blood flow to relevant regions of the brain.